The HTML tags <blink> and <marquee>, as you probably know, should never be used.

"Note. If blinking content (e.g., a headline that appears and disappears at regular intervals) is used, provide a mechanism for stopping the blinking. In CSS, 'text-decoration: blink' will cause content to blink and will allow users to stop the effect by turning off style sheets or overriding the rule in a user style sheet. Do not use the BLINK and MARQUEE elements. These elements are not part of any W3C specification for HTML (i.e., they are non-standard elements)."

So far, I like CSS2.1's statement best. I've not really made up my mind about whether or not CSS3 should include blink; on one hand, it follows the philosophy of separating style from content; on the other hand, it's a usability issue. Blinking text is simply annoying. On the gripping hand, people can enable their user style sheets and override it by doing text-decoration: none;. So I'm honestly not sure.

In addition to this, CSS3 currently has a marquee property. Whether this is a good thing is also debatable. At least it seems to be well thought out.